1. Field of the Invention
The present invention relates to image processing, and in particular relates to devices and methods of image compression and decompression for synthetic images
2. Description of the Related Art
The rapid growth of digital imaging applications, including desktop publishing, multimedia, teleconferencing, and high-definition television (HDTV) has increased the need for efficient and standardized image compression techniques. Without image compression, the transmission of images would require an unacceptable bandwidth for many applications. As a result, methods of compressing images have been the subject of numerous research publications. Image compression schemes convert an image consisting of a two-dimensional array of pixels into a sequence of bits which are transmitted over a communication link. Each pixel represents the intensity of the image at a particular location therein. The transmission link may be an ordinary telephone line.
Consider an image comprising a gray-scale representation of a photograph at a resolution of 1000×1000 lines. Each pixel typically consists of 8 bits which are used to encode 256 possible intensity levels at the corresponding point on the photograph. Hence, without compression, transmission of the photograph requires that 8 million bits be sent over the communication link. A typical telephone line is capable of transmitting about 9600 bits per second; hence the picture transmission would require more than 10 minutes. Transmission times of this magnitude are unacceptable.
As a result, image compression systems are needed to reduce transmission time. It is also apparent to those skilled in the art that image compression systems may also be advantageously employed in image storage systems to reduce the amount of memory needed to store one or more images.
Further, there are two kinds of images, natural images and synthetic images. In general, high frequency components only occur in luminance domain for natural images. Contrary to natural images, high frequency components occur in both of luminance and chrominance domains for synthetic images. Due to synthetic images having more high frequency components than natural images, it is more difficult to compress synthetic images than natural images.